A vintage (and seemingly mint condition, still in the original box) Westinghouse type ST-35 Ammeter, Style PH-40151-3 with a rating of 0-10 Amps. Not sure on its exact age, but the logo on the box was in use from 1936-1960, and judging from the style of the sticker, we'd estimate it's probably closer to the older end of that range, possibly a surplus from war effort production. Seems to have been intended for use with radios somehow.